I do not see a disk problem, but I observe high (60-85%) CPU / Mem usage with downgrading upload traffic and delays in UI of other processes: http://forum.utorrent.com/viewtopic.php?pid=642860#p642860 (2 pictures of CPU/Mem/IO usage by one uTorrent process with a difference of 1 day). For now I closed uTorrent due to I can't solve this problem quickly.